Thermostatic control device



Jan. 23, 1934 J. G. MONAMARA THERMOSTATIC CONTROL mavzcw INVENTO/B 2 Sheets-Sheet 1 Illlllllll III I Filed .July 18 19:52

| r l I I I I I l l llllll Jan. 23, 1934. McNAMARA 1,944,358

THERMOSTATIC CONTROL DEVICE Filed July 18, 1932 2 Sheets-Sheet 2 rg' .5. 10 1 1 F .8. 60 F 10 er" @1 57? 5.7, 57

38 q f 1 31 3 37 w i q 42 43 28 55 INVENTOR Patented Jan. 23, 1934 pmrso STATES PATENT QFFICE THERMOSTATIC CONTROL DEVICE James G. McNamara, Brooklyn, N. Y., assignor to Mergenthaler Linotype Company, a corporation of New York This invention relates to "thermostatic control devices; and while it may be used in connection with various kinds of heating apparatus, it is herein described and illustrated in association with the heated metal pot of a slug casting or linotype machine.

The present invention provides a thermostatic control which is thoroughly reliable and efliclent in operation, and which is durable and economical in construction, having few and simple parts conveniently and compactly arranged and not liable to get out of order.

A preferred embodiment of the invention possessing the characteristics noted includes a movable contact arm ior turning on and off the supply ofenergy for the heating apparatus, a thermal couple comprising a tube and an expansion element in the form of a rod housed therein, and a plurality of interacting multiplying levers arranged between the contact arm and the expansion rod and normally disposed to maintain the contact arm in active or on position. Each lever is so fulcrumed as to present a very short arm and a relatively long arm, so that a slight elongation of the expansion element or rod will be multiplied many times in its eiiect on the contact arm. In addition, the arrangement of the parts is such that the action of the contact arm is rendered positive, and in one form of the device instantaneous.

In carrying out the invention, rigid levers are provided and are pivota ly connected to rigid supports by means of blade springs which serve as fulcrums therefor. Further, a positive connecting link is provided between the levers, and the contact arm is carried by the second multiplying lever rather than being independently mounted.

In the accompanying drawings:

Fig. 1 is aside vie parts being broken away, or" a preferred embodiment of the invention, shown in association with an electrically heated .rnetal pot of a slug casting machine;

Fig. 2 is a sectional view of a portion of the thermal couple employed in the invention, and of its connection with the lever system of the device;

Fig. 3 is a sectional view of the lower portion of the thermal couple;

Fig. 4 is a sectional view taken on the line 4-4 of Fig. 3;

Fig. 5 is a front elevation of a preferred em bodiment of the invention, showing by-the full lines the form of the device used in conjunction with an electric heater, and showing by the broken lines a part oi a modification thereof, for use with a gas heater;

Fig. 6 is a plan view, partly in section, showing the electric switch elements of the improved device; 7

Fig. 7 is a vertical sectional view through the electric switch, showing the internal construction thereof; and

Fig.8 is a. vertical sectional view, showing the internal construction of the modification of the improved device shown in part by the broken lines in Fig.6.

Describing the invention in detail, there is shown in Fig. 5 in full lines a preferred embodiment of the invention, adapted for use with an electric heater. This embodiment, which will be described first, includes a casing l0, provided with a suitable removable cover ill and having near its lower end a hollow boss 11 (see also Fig. 1), in which is detachably secured, as by a nut 14, a tube or housing 12 having a low co eflicient of expansion, said housing having a closed base in and being open at the top. As shown in Figs. 3, 4 and 5, there is mounted in the housing 12 the expansion element or rod i6 oi the thermal couple, which has a relatively high coefficient of expansion. In the present instance, the expansion rod 16 is made of aluminum, being provided at its upper and lower ends with tips 17 and 18, respectively, made of a metal of a harder and less expanslble nature, such as steel, which tips are seated in recesses formed in opposite ends of the rod 16 and detachably secured thereto by pins 1'? and 18 respectively, (see Figs. 2 and 3), in order better to with 00 stand wear and strain. The rod ie, which, as already stated, is arranged within the non-expansible housing 12, is anchored therein by the pin 18, it being seated firmly on the base 12 of the housing and adapted to expand upward- 96 ly. In order that the heat may act upon the rod '16 most eiiectively, the housing 12 ls'cut away on opposite sides, as at 12 thus exposing the rod 16 directly to the source oi heat.- Further reference will be made to the rod 16 at a roe later point.

The contact arm upon which this expansion rod 16 acts, through intermediate agencies pres ently to be described, and which arm effects the control of the flow 01 electric current to a heater, not shown, includes a spring arm is, carried by one of the levers already alluded to, and pro- 7 vided at its lower end with a roller head 21, which is adapted to rock over the thin edge 22.01 an electric contact 23, see Figs. 5 and As this BIL " when moved to the other side, with an electric contact point 26, these contacts 23, 24, and 26 being connected to the electric terminals L, C and H, respectively, as shown in Figs. 5 and 6. Normally, the roller head 21 is wedged between and arranged to bear against one side face 23' of the contact 23 and the contact point 24, see Figs. 6 and 7, in whichposition the current is turned on to the electric heater, and when the roller head is rocked over the edge 22 it is adapted to be wedged between and to bear against the other side face 23 of the contact 23 and the contact point 26, the current then being turned off so that the supply of heat ceases.

Between the expansion rod 16 and the contact arm 19 is arranged in vertical position, a pair of multiplying levers 27 and 28, at least one of said levers, preferably the lever 28, being formed of material which is a non-conductor of elec tricity. The levers 27 and 28 are respectively pivotally connected or fulcrumed by means of blade springs 29 and 31 to rigid supports 32 and 33, provided near the lower and upper ends, respectively, of the casing 10. The spring 29, see Fig. 5, is fastened securely to the lever 27 and .its rigid support 32 by means of a pair of plate clamps 34 and 36, respectively, which are held in place by screws, not shown. Similarly, the blade spring 31 is secured to the lever 28 and its rigid support 33 by means of plate clamps 3'7 and 38, respectively. In this way not only are the springs securely fastened to the rigid supports, but the fulcrum point of each of the levers 27 and 28 is kept constant and free from possi-- ble variation due to insecure connections of the blade springs to their respective supports. Moreover, by employing these fiat blade Springs as pivots for the levers, the vibration oi. the casing 10, to which the supports are rigidly attached, will be absorbed thereby and will not aiIect unfavorably the operation of the device. Further, with such pivots lost motion is avoided, as well as wear of parts and the development of loose connections, and other defects inherent in various usual forms of pivotal mountings having relative movement between their parts are obviated. This feature is very important in the present construction where precision and certainty of performance are demanded.

The blade springs 29 and 31 perform yet another important function in acting always to maintain the multiplying levers 27 and 28 in normal position, doing away with special springs attached to and acting upon the levers in opposition to the expansion of the rod 16. In this respect, the blade springs are most desirable since they act always to maintain the levers in normal (in this instance vertical) position regardless of whether the rod 16 remains in contact with or moves out of engagement with the lever 27 as it contracts.

The upper arm 39 of the lever 27 has secured thereto a blade member 41, see Fig. 5, extending beyond the end of said arm and being bifurcated at its upper end. Between the yoke arms formed at the end of the blade 41, there is pivoted on a suitable pin 42 a link 43, which in like fashion is pivoted at its other end on a pin 44 extending between a pair of raised bosses formed near the upper end of the lever 28, thus providing a positlve connection between the levers. In order to obviate imperfectoperation of the device due to the development of loose connections at the pivotal points of the link 43, a tension spring 47 is secured, as shown in Fig. 5, to the long arm 39 of the lever 27 and to the lever 28, which spring acts constantly to draw, the levers 27 and 28 toward each other in opposition to the connecting link 43 and thus maintain the levers in their proper spaced relation. Of course, a compression spring could be substituted for the tension spring 47, which would act constantly to spread the levers apart in opposition to the connecting link 43, and the variation in the operation of the device resulting from such substitution of springs could be corrected by adjusting means to be described later.

Here it may be noted that the spring contact arm 19 is adjustably mounted on the lever 28 by means of a clamp 45 (see Fig. 7 fastened to the lever near its lower end, the end of the spring being looped under the clamp for that purpose. This adjustability of the arm 19 permits the proper alignment of the roller head 21 of the arm 19 with the contact points 24 and 26.

It will noted that the short arm of the lever 27 (the horizontal distance between the center of the tip 17 of the expansion rod 16 and the fulcrurn point of the lever 27) is quite short and in comparison therewith the arm 39 of the lever, extended by the blade 41, is very long, thus multiplying many times the expansive movement of the rod 16. In like manner, the short arm of the lever 28 (the vertical distance between the pivot pin 44 and the fulcrumpoint of the lever 28) is very short as compared with the long arm of said lever, so that the movement transmitted from the lever 27 through the connecting link 43 to the lever 28 is multiplied many times in its transmission through the long arm thereof to the roller head 21. Under the gradual pressure exerted upon the lever 28, due to the expansion of the rod 16, the spring contact ,arm 19 bends, until finally the roller head 21 suddenly snaps out of its active or on position, as shown in Fig. 5, and makes contact with the other side face 23 of the contact 23 and the contact point 26 to shut oil the electric current, the spring arm 19 resuming its normal straight condition. On the other hand, when and as the rod 16 gradually contracts to normal length because of the decrease in temperature of the heated medium due to the heat being shut oil, the spring arm 19 will be bent gradually to the left until it will as suddenly snap the roller head 21 back into its normal or on position, as shown in Fig. 5. The device, therefore, in this particular embodiment, is especially efficient and adaptable for use with mechanisms in which instan taneous turning on or off the heat is necessary or desirable.

It is highly desirable that the device he made adjustable in order to meet varying conditions of use, and with this end in view the lower offset end of the lever 27, see Figs. 2 and 5, is formed to receive a stud 48 having a threaded upper portion 49, by means of which the stud 48 can be adjusted vertically toward or away from the tip 17 of the {expansion rod 16, the said stud being held in any adjusted position by a lock nut 51, all as clearly shown in Fig. 2. As shown in this figure, the 'rod 16 is in expanded condition, with its tip abutting against the lower end of the stud 48 to actuate the lever system, as hereinbeiore described. If,

however, it is desired to alter the operating range of the device, the stud 48 can be adjusted a desired distance toward or away from the tip 17 of the expansion rod 16, so that the latter must expond to a lesser or greater degree in order to contact with the lower end 0! the stud.

Further to regulate the action of the thermal device and to eifect a much finer adjustment thereof, the upper part of the blade 4.1 is formed with an aperture 52 therethrough, in which is disposed a thumb screw 53, adapied to press against the long arm 39 oi the lever 27. Thus, it will be seen that by moving the blade ii to and from the arm 39 by appropriate turnings of the thumb screw 53, the pivot link as, will assume varying angular positions between the levers 27 and 28, and in so doing shortening or lengthening its operative length by bringing the levers somewhat nearer together or spacing them furl-her apart, with the result that the operative action of the levers will be diminished or increased. For convenience, the handleoi the thumb screw 53 is milled, and a leaf spring 54, which is fastened to the blade 41, is provided with a projecting rib 55 adapted to lit in the spaces between the ribs of the milled handle. In this manner, the thumb screw 53 is prevented from moving in response to any tremors of the machine, and the fine adjustment of the thermal device preserved.

The operation of this preferred embodiment of the device will now be briefly described. As the temperature of the heated medium in which the expansible rod is is immersed reaches the predetermined range of temperatures through which the device is adapted to operate, the rod 16 expands. Due to the fact that the lower end of the rod it rests on the solid base 12 of the housing 12 in which it is enclosed, the elongation of the rod is .in one direction only, namely, up-

wardly. As the rod 16 elongates, i's tip 17 con-' tacts with the lower. end of the adjustable stud 48 in the offset portion of the lever 27, continued elongation of the rod rocking the lever about its pivotal point or fulcrum, whereby the long arm 39 of the lever is moved toward the right. This movement of the lever 27, through the positive connection as, rocks the lever 28 aboutv its pivotal "point or fulcrum, moving this lever also to the right. The movement of the two levers 27 and 28 is as steady and gradual as the elongation of the expansion rod 16, but this gradual move ment, instead of rocking the roller head 21 slowly from one contacting position to anothenbends the spring contact arm 19 to the right until the tension of said spring arm becomes suillcient suddenly to snap the roller head 21 over the thin edge 22 of the contact 23, whereby the electric current is instantly shut off. As the temperature of the heated medium lowers, due to the supply of heat being shut off, the levers gradually move to the left as the expansion rod 16 contracts, the spring contact-arm l9 bending to the let: until its tension becomes sufficient to snap the roller head 21 back. to its normal or on position.

In Figs. 5 and 8 there is shown a modification of the device particularly adapted for use with gas or other fluid fuel heaters. in this enihodh merit, a valve casing 57 is secured to the rear wall of the casing is by means of screws lid and 59 which pass through a side wall oaprojecting from the valve casing and formed with lateral elongated recesses 61 and s2. reference will he made to this torture or the device.

The valve casing 57 is formed near one end with a cylindrical recess 57 passing entirely through the casing, the walls defining the recess ,loeing screw threaded the openings thereoi to receive the threaded ends of fuel sup-ply pipes. In the present case, however, only one supply pipe 69 leads to the recess 57", the opposite end or said recess being closed by a screw plug 60. A second cylindrical recess 57 is formed in the casing 57, extending only a little more thanhalf way therethrough and opening through the same side of the casing to which the fuel supply pipe 69 is connected. The walls of the casing 57 which define the recess 57 are also screw-threaded near the opening of the recess, which screw threads are adapted to receive the threaded end of a feed pipe 71 leading to the burner or heater, not shown. The two recesses 57 and 57 are parallel with" one another and communicate by means of a third cylindrical recess 57, disposed at right angles thereto, the recess 57 being localed centrally of the valve casing 57, and to which reference will be made later.

The end of the valve casing 57 adjacent the casing 10 of the thermostat unit is formed with a recess 64, of larger diameter than the recesses already described, in which a centrally drilled screw-threaded plug 64 is adapted to be fitted, the recess 64 opening into the recess 57 and being in alignment with the communicating recess 57. At its opposite end, the casing 57 is formed with a projecting boss 66, in which is formed a recess 66 opening into the recess 57 and being in alignment with the communicating recess 57.

The valve, in the present instance, comprises a rod 73, one end of which is slidably suppormd in the recess 66 formed in the boss66, while the opposite end thereof is slidahly supported in the recess formed in the plug 64; the said boss and plug forming bearings for the rod 73. The end of the rod 73 supported in the plug 64 projects therethrough and into the interior of the casing 10 in abutting relation with an actuating member or blade 7 5 secured to the lever 28 of the thermostat unit. This relation of the end of the rod 73 and the blade 75 is maintained by the pressure or a compression spring 76, located in the recess 66 and exerting pressure against the contiguous end of the rod 73, the spring seating against the end of an adjusting screw 67 locked by a nut 68 in the end of the boss 66, and by means of which screw the pressure of the spring maybe varied. In order properly to set the end of the rod 73 with relation to the actuating blade 75, the entire valve casing 57 is movable endwise within the limits of the elongated recesses 61 and 62, to which reference has already been made.

About midway 01' its length the rod 73 is formed with a valve head 77, of slightly larger diameter than the communicating recess 57% This valve head 77 is adapted to be carried by the rod 73, under the influence of the blade 75, toward or away from the opening of the recess 57, which is in the form of a valve seat 77, in a manner and for a purpose presently to he described. it

may be noted that, in assembling the parts, the

rod 73 carrying the valve head 77 is entered through the recess dd, which is sufiiiciently large to permit passage of the valve head 77 therethrougli, the plug 64 being then screwed in pit-we.

operation oi? this modification the vice will now he described. illustrated in 8, the valve in closed condition with the valve head 77 covering the opening or" the conrmimi eating recess 57. For purposes of description, it

will be assumed the valve head 7? is in open then through the feed pipe 71 to the burner, not shown. As the temperature of the heated niedium rises, the thermostat unit operates as previously described, in connection with an electric heater. However, instead of actuating a contact arm, the lever 28, through the blade 75, gradually and steadily moves the slidable rod 73 toward the right, compressing the spring 76, the move ment of the rod 73 carrying the valve head 77 into closer and closer proximity to the valve seat 77. Thus the supply of fuel flowing through the communicating recess 57, and eventually to the burner, is gradually diminished and the flame of the burner slowly lowered. When, due to the lowered heat, the temperature of the heated medium falls and the lever 28 moves to the left, as previously described, carrying the valve actuating blade 75 with it, the rod 73 is also moved to the left and maintained in its abutting relation with the blade 75 by the pressure of the compression spring 76 thereon. As the rod 73 moves to the left, carrying the valve head 77 with it away from the valve seat 77*, an increasing supply of fuel is by-passed and the high flame of the burner is gradually restored.

It should be noted that in practice the valve head 77 never closes against the valve seat 77 completely to shut off the supply of fuel, since, as the temperature of the heated medium approaches the desired point, the flame of the burner is gradually lowered until it reaches a point where it keeps the said medium at the proper temperature, and thereafter the fluctuations of the valve head ,77 are slight. It may be pointed out, however, that by the use of a pilot burner it is possible to employ a snap action form of valve which quickly moves away from and closes against the seat 77*, whereby the,burner is instantly turned on and off, respectively, at the upper and lower points of a predetermined range of temperatures. Such form of valve would still be within the scope of the invention. 5

The device has been described thus far as applicable to any heating device for which it is adapted but, as previously stated, it is exceptionally well adapted for use with the melting pot of a slug casting or linotype machine, and it will now be briefly described as associated with such device. Preliminarily, however, it may be noted that in order to obtain proper results in casting printing slugs, the metal should be maintained in a molten condition, heated to a degree ranging between certain narrow temperature limits, as between 535 and 550 F. In actual practice, however, and for reasons well known in the art, the temperature of the heated metal, unless otherwise controlled, will outrange in both directions the narrow limits thus prescribed. It is apparent, therefore, that a thermostatic control device for a heater associated with the melting pot of a slug casting machine, in order to function in a manner properly to meet the requirements thereof, should be positive and accurate in its operation, so that the supply of heat to the melting pot can be delicately regulated as the condition of the heated metal may require. Further, it is pointed out that preferably the normal setting of the device in association with the melting pot is one in which the control of .the melting pot heater is such that the supply of heat is suspended only when the temperature of themolten metal becomes too high.

The device is shown in Fig. 1 as securely mounted upon the melting pot 80 of a slug casting machine and so arranged that the lever 28 carrying the contact arm will reciprocate in a direction at right angles to the direction of the pivotal movement of the melting pot, which is from left to right as shown in said Fig. 1. heating the melting pot from a source of electrical energy, there is mounted on the pot a terminal block 82 of a pair of electric heaters, not shown, and hereinafter referred to as the heater. In this block, wires 84 from the heater are connected to the pot heater terminals, not shown, the cur rent being turned on and off by a switch in the circuit, also not shown, it being unnecessary for an understanding of the instant invention to illustrate or describe these familiar details. Wires 86 lead from the heater to the contacts L, C, H, which are housed in a terminal block 7, previously described, and which are arranged partly in the casing 10, the roller head 21 carried by the arm 19 making and breaking the connection between these several contacts, all as previously described.

The invention, in its broader aspects, is not limited to the precise construction shown and described, as many changes may be made in the details thereof without departing from the spirit of the invention. It is to be understood, therefore, that the invention is not limited to any speciiic form or embodiment, except insofar as such limitations are specified in the appended claims.

Having thus described my invention, what I claim is:

1. A thermostatic device including, in combi nation, an actuating member, a thermal couple having an expansion rod, a pair of rigid multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, a rigid link pivotally connected to the first lever at the latters end remote from its pivot point and to the second lever near the latter's pivot point, rigid supports for the levers, and blade springs pivotally connecting. the levers to their supports, and a tension spring connected at its opposite ends to the two multiplying levers and acting constantly to draw them toward each other in opposition to the connecting link.

2. A thermostatic device including, in combination, an actuating member, a thermal couple having an expansion rod, a pair of rigid multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, the actuating member being carried by the second of the levers, a rigid link positively connecting the levers, rigid supports for the levers, blade springs pivotally connecting the levers to their supports, and a tension spring connected at its opposite ends to the two multiplying levers and acting constantly to draw T them toward each other in opposition to the connecting link.

3. A thermostatic device including, in combination, an actuating member, a thermal couple having an expansion rod, a plurality of rigid multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, rigid supports for the levers, blade springs pivotally connecting the plying levers disposed between the actuatin member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, a rigid link pivotally connecting the levers, rigid supports for the levers, blade springs pivotally connecting the levers to their supports, one of said levers being provided with a blade extending beyond the end of said lever and to which the pivotal connection of the link is made, and means for varying the relation of said blade to its associated lever, whereby the effective length of the link can be varied.

5. A thermostatic device including, in combination, an actuating member, a thermal couple having an expansion rod, a pair of rigid multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, a rigid link pivotally connecting the levers, rigid supports for the levers, blade springs pivotally connecting the levers to their supports, one of said levers being provided with a resilient blade extending beyond the end of said lever and to which the pivotal connection of the link is made, and an adjusting screw for setting the resilient blade at different distances from its associated lever'to vary the effective length of the connecting link.

6. A thermostatic device including, in combination, an actuating member, a thermal couple having an expansion rod, a pair of co-acting rigid which one end of said link is connected, the resilient means being adapted to vary the effective length of the link.

7. A thermostatic device including, in combination, an actuating member, a thermal couple having an expansion rod, a pair of spring-actuated multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, supports on which the levers are pivotally mounted, a link positively connecting the levers, and a spring element associated with the levers and acting constantly to maintain said levers in their proper spaced relation.

8. A thermostatic device including in combination, an actuating member, a thermal couple having an expansion rod, a pair of rigid springactuated multiplying levers disposed between the actuating member and the expansion rod and arranged to operate the actuating member by the expansion and contraction of the rod, one of said levers being a non-conductor of electricity, rigid supports for the levers, blade springs pivotally connecting the levers to their supports, said blade springs tending constantly to maintain the levers in normal position, a screw for varying the operative relation of the levers and the expansion rod, a rigid link pivotally connecting the levers, one of said levers being provided with a resilient blade extending beyond the end of said lever and to which the link is pivotally connected, an adjusting screw for setting the resilient blade at difierent distances from its associated lever to vary the effective length of the connecting link, and a. tension spring connected at its opposite ends to the two multiplying levers and acting constantly to draw them toward each other in opposition to the connecting link.

JAMES G. MCNAMARA. 

